Add `ServiceRequest::extract`

actix-web/CHANGES.md

@@ -1,7 +1,7 @@
 # Changes
 
 ## Unreleased - 2021-xx-xx
-
+- Add `ServiceRequest::extract` to make it easier to use extractors when writing middlewares.
 
 ## 4.0.0-rc.3 - 2022-02-08
 ### Changed

actix-web/src/extract.rs

@@ -18,6 +18,9 @@ use crate::{dev::Payload, Error, HttpRequest};
 /// A type that implements [`FromRequest`] is called an **extractor** and can extract data from
 /// the request. Some types that implement this trait are: [`Json`], [`Header`], and [`Path`].
 ///
+/// Check out [`ServiceRequest::extract`](crate::dev::ServiceRequest::extract) if you want to leverage 
+/// extractors when implementing middlewares.
+///
 /// # Configuration
 /// An extractor can be customized by injecting the corresponding configuration with one of:
 ///

actix-web/src/service.rs

@@ -24,7 +24,7 @@ use crate::{
     guard::{Guard, GuardContext},
     info::ConnectionInfo,
     rmap::ResourceMap,
-    Error, HttpRequest, HttpResponse,
+    Error, HttpRequest, HttpResponse, FromRequest
 };
 
 pub(crate) type BoxedHttpService = BoxService<ServiceRequest, ServiceResponse<BoxBody>, Error>;
@@ -95,6 +95,31 @@ impl ServiceRequest {
         (&mut self.req, &mut self.payload)
     }
 
+    /// Use an [extractor](crate::FromRequest) to build a type out of the incoming request.  
+    /// 
+    /// `extract` is particularly handy when you need to use an extractor inside 
+    /// a middleware implementation.
+    /// 
+    /// # Example
+    /// 
+    /// ```rust
+    /// use actix_web::dev::{ServiceRequest, ServiceResponse};
+    /// use actix_web::web::Path;
+    /// use actix_web::Error;
+    /// 
+    /// fn f(service_request: ServiceRequest) -> Result<ServiceResponse, Error> {
+    ///     let path: Path<(String, u32)> = service_request.extract()?;
+    ///     // [...]
+    /// #   todo!()
+    /// }
+    /// ```
+    pub fn extract<T>(&mut self) -> <T as FromRequest>::Future
+    where 
+        T: FromRequest
+    {
+        T::from_request(&self.req, &mut self.payload)
+    }
+
     /// Construct request from parts.
     pub fn from_parts(req: HttpRequest, payload: Payload) -> Self {
         #[cfg(debug_assertions)]